One watt/one amp no-fire match type initiator

ABSTRACT

A match type electrical initiator which has a 1 watt/1 amp nofire characteristic utilizes an insulated dual conductor flat cable, such as polystrip cable, as an integral part. The initiator has a head portion and a body portion, the body portion being the insulated dual conductor cable whose conductors terminate in the head portion. The head portion is comprised of the conductors which have been bared of insulation, fitted with a bridgewire fastened therebetween, covered with an ignition material with about 90% by weight of the material being comprised of a stoichiometric mixture of lead thiocyanate, potassium chlorate, and charcoal and with about 10% by weight of the material being a binder, and covered with an external epoxy adhesive coating which serves to seal the head portion thereby obviating the requirement of an initiator case. The initiator can be manufactured in mass production to a thinness of about 0.070 inch which makes it ideally suited for initiating action of a destruct unit for rocket motor cases for weather rockets. The small initiator can be easily fitted into the approximate 0.100 inch space envelope of the honeycomb of a rocket motor case.

United States Patent Stevens Oct, 7, 1975 1 ONE WATT/ONE AMP NO-FIREMATCH TYPE INITIATOR [75] Inventor: Philip M. Stevens, Salt Lake City,

Utah

[73] Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

[22] Filed: Apr. 4, 1974 [21] Appl. No.: 457,861

[52] U.S. Cl 102/28 M [51] Int. Cl. F42B 3/12 [58] Field of Search102/28 R, 28 M; 149/18, 149/24, 27, 28

{56] References Cited UNITED STATES PATENTS 1,798,332 3/1931 Littlebury149/27 X 1,935,495 11/1933 Young 102/28 M 2,506,229 5/1950 Lowe et al.102/28 M 2,995,780 8/1961 Scott 102/28 M 3,055,780 9/1962 Finnegan eta1. 149/27 3,291,046 12/1966 Dahl t 102/28 'IZb [ ABSTRACT A match typeelectrical initiator which has a l watt/l amp no-fire characteristicutilizes an insulated'dual conductor flat cable, such as polystripcable, as an integral part. The initiator has a head portion and a bodyportion, the body portion being the insulated dual conductor cable whoseconductors terminate in the head portion. The head portion is comprisedof the conductors which have been bared of insulation, fitted with abridgewire fastened therebetween, covered with an ignition material withabout 90% by weight of the material being comprised of a stoichiometricmixture of lead thiocyanate, potassium chlorate, and charcoal and withabout 10% by weight of the material being a binder, and covered with anexternal epoxy adhesive coating which serves to seal the head portionthereby obviating the requirement of an initiator case. The initiatorcan be manufactured in mass production to a thinness of about 0.070 inchwhich makes it ideally suited for initiating action of a destruct unitfor rocket motor cases for weather rockets. The small initiator can beeasily fitted into the approximate 0.100 inch space envelope of thehoneycomb of a rocket motor case.

2 Claims, 1 Drawing Figure U.S. Patent 0a. 7,1975

////A7/// V w ONE WATT/ONE AMP NO-=lFllRE MATCH TYPE TNllTIATORBACKGROUND OF THE INVENTION The most vulnerable components of a weaponspropulsion system is generally agreed to be the initiators. Theseinitiators are most commonly called electroexplosive devices. Theiractivation is by the application of electric energy, through conductorsinto a resistive element which is called a bridge which converts theelectric energy into other energy forms. This conversion is primarily toheat, but sometimes may be in the form of high velocity particles orvapors and plasmas at high pressure. These initiators are susceptible toaccidental initiation when the applied energy through the bridge isexceeded above where the item is designed to function. As an example, anelectric initiator designed to fire at /2 amp current through thebridge, will fire at this point and above, regardless of the source fromwhich the energy is emitted. A nuclear device generating anelectromagnetic pulse (EMP) which would induce a current in the bridgeto above 1% amp would then cause the item to be activated. The items arealso susceptible to accidental initiation from electrostatic energiesimparted into the bridgewire or imparted through the explosive mixtures.

Because of military safety requirements, standards have been set whichrequire a specified rriinimum value of amperes or watts to which aninitiator can be subjected to without firing. A small initiator of thematch type is difficult to construct with an ampere all-fire ratingwhich exceeds about /2 ampere or approximately 4 watt.

Prior art match type initiators have been constructed with an all-firerating of ampere or approximately A watt. These initiators have athickness of about 0.120 inch. Because of the manner of construction,the thick ness and the all-fire rating have been accepted as the bestthat can be delivered Within the state-of-the-art.

Desirable is an initiator of the match type which possesses the onewatt/one amp no-fire characteristics.

Also desirable is an initiator of the match type which can be made asthin as 0.070 inch thickness to enable it to be positioned within thehoneycomb structure of a consumable rocket motor case.

Therefore, an object of this invention is to provide a match typeinitiator which possesses the one watt/one ampere no-firecharacteristics.

Another object of this invention is to provide a match type initiatorwith a thickness of about 0.070 inch.

A further object of this invention is to provide an initiator which canbe manufactured in mass production and which does not require aseparately made outer case.

SUMMARY OF THE INVENTION The initiator of this invention is of the matchtype having a head portion and a body portion. The initiator iscomprised of a dual conductor flat cable having conductors which extendthrough the body portion and terminate in the head portion. Theconductors are bared of insulation in the head portion for apredetermined distance from the end of the flat cable, a bridgewire(pyrofuze) is soldered between the spaced apart conductors, a coating ofignition material is applied to the conductors and bridgewire, and acoating of an external epoxy adhesive is applied to the ignitionmaterial which coating serves to seal the head portion and to functionas the initiator case.

The match type initiator of this invention possesses a 1 watt/1 ampno-fire characteristic. The initiator can be manufactured to a thinness.of about 0.070 inch with a head portion that extends about A; inch fromthe body portion which may have an optional length. The conductors maybe bared of insulation at the opposite end from the head portion for onetype of installation to an electrical power source.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE of the drawing is asectional view of the match type initiator of this invention.

DESCRIPTION OF THE PREFERRED ElVIBODIMENT The match type initiator ofthis invention is comprised of a pyrofuze bridgewire soldered between abared length of the conductors of a dual conductor flat cable andcovered with an ignition material with about by weight of the materialbeing comprised of lead thiocyanate, potassium chlorate, and charcoaland with about 10% by weight of the material being a binder. An externalepopxy adhesive coating seals the initiator thereby obviating therequirement of an initiator case.

The drawing shows a match type electrical initiator 10 of this inventionthat is comprised of an insulated dual conductor flat cable 12 having ahead portion 12a and a body portion 12b. The conductors 14 extendthrough the body portion and terminate in the head portion. The bodyportion includes insulation means 16 for covering the conductors. Abridgewire 18 is fastened between the conductors in the head portion. Anignition material 20 covers the head portion which is sealed with anexternal epoxy adhesive coating 22.

The dual conductor fiat cable which is shown in the trade as polystripcable is preferred for use in this invention since it has the dimensionsof about 0.310 inch wide and about 0.010 inch thick along with dualcopper conductors with each conductor being about 0.045 inch wide, about0.003 inch thick and having the proper line resistance of 0.07 ohm perfoot of conductor. The head portion of the finished initiator can bemanufactured to a size which is only 0.070 inch thick thereby making itideally suite-d for its intended use to initiate destruct action in aweather rocket motor case or a rocket motor case for similar use. Theinitiator can be positioned within the approximate 0.100 inch spaceenvelope of the honeycomb structure of a rocket motor case. Since theinitiator has a 1 watt/1 ampere no-fire characteristic it offers a highsafety factor required for military use. The initiator of this inventioncan be manufactured to a size of about the size of available match-typeinitiator which has an all-fire rating of Va ampere and approximately/1. watt. In actual testing of the match-type initiator of thisinvention the assembly requires in excess of 3 amperes or 1.78 watts toinitiate.

The general procedure followed in preparing the dual conductor,soldering the bridge, and the coating and forming matchhead, and curingcoating for the initiator include:

1. baring the dual conductors about 0.125 t 0.025 inch, from end, forhead portion, use solder gun to prevent insulation from unraveling;

2. soldering pyrofuze bridgewire between conductors;

3. coating of bridge and conductors to form a matchhead: sufficientbutyl acetate is added to ignition material (pyrotechnic) and binder toinsure complete coating of bridge and conductors, followed by drying at120F for 12 hours; and,

4. coating with epoxy adhesive (4 parts) and 1 part amine curing agentor activator which allows coating to be thin enough to remove excess bydipping and following by curing at 120F for 12 hours. The coating ofbridge and conductors to form a matchhead may be accomplished bybrushing the pyrotechnic and binder or by dipping to insure completecoating. A further description of the preferred binder, adhesivecoating, and their respective functions are given below.

A preferred binder material for use with the ignition material of thisinvention contains a solid material, lead styphanate, which contributesto the reaction plus an appropriate amount of Egyptian lacquer, wellknown in the initiator art. A ratio of 2 grams of lead styphanate toabout 1.2 cubic centimeters of Egyptian lacquer or similar compositionprovides a suitable consistency. The Egyptian lacquer contains about 3-4parts of dewaxed bleached shellac, 0.0190.025 parts of oxalic acid,about 95-105 parts nitrocellulose, about 12.5-14.5 parts non-volatilesolvent, and about 84.5-87.5 parts of mixed solvent comprised of one ormore parts each of denatured ethanol, isopropyl alcohol, methylisobutylcarbinol, butyl alcohol, methyl ethyl ketone, methyl isobutyl ketone,toluol, and xylol. The non-volatile solvents can be those which are wellknown in the paint and varnish art which serve as hardener and bindersfor the solids.

The function of the binder material serves to fix the lead styphanateand ignition material to the conductors and bridgewire. The function ofthe epoxy adhesive is to form a seal for the ignition material and toserve in the function of the ignitor case. The epoxy adhesive is curablewith an amine curing agent for epoxy adhesive. Epoxy adhesive 4 parts toabout 1 part of amine curing agent is used.

When the electrical power source is applied to the initiator, thebridgewire undergoes reaction which supplies heat to cause a rapidrelease of energy which is accelerated by the lead styphanate to promoteburning of the ignition material. The results produce a controlledrelease of energy from the initiator after the one watt/one amperevalues are exceeded. Generally, the assembly requires about 3 amperes orabout 1.78 watts to initiate which makes this initiator far exceed the 1watt/1 ampere no-fire characteristic to thereby provide a high safetyfactor as required for military use.

I claim:

1. A match type electrical initiator comprising:

i. an insulated dual conductor flat cable having a head portion and abody portion, said conductors extending through said body portion andhaving first ends terminating in said head portion;

ii. insulating means covering said body portion;

iii. a bridgewire fastened between said conductors in said head portion;

iv. an ignition material covering said head portion, and ignitionmaterial being comprised of about by weight of a stoichiometric mixtureof lead thiocyanate about 35.6 parts, potassium chlorate about 44.4parts, and charcoal about 20.0 parts, and of about 10% by weight of abinder material comprised of lead styphanate in ratio of about 2 gramsto about 1.2 cubic centimeters of a lacquer formulated of about 3-4parts of dewaxed bleached shellac, of about 0.0l90.025 parts of oxalicacid, of about 9.5-10.5 parts nitrocellulose, of about 12.514.5 partsnon-volatile solvent, and of about 84.5-87.5 parts of a mixed solventcomprised of one or more parts each of denatured ethanol, isopropylalcohol, methylisobutyl carbinol, butyl alcohol, methyl ethyl ketone,methyl isobutyl ketone, toluol, and xylol; and, 1

v. an external epoxy adhesive that is curable with an amine curing agentfor coating and for sealing said ignition material.

2. The match type electrical initiator of claim 1 wherein saidconductors have second ends terminating outside said body portion.

1. A MATCH TYPE ELECTRICAL INITIATOR COMPRISING: I. AN INSULATED DUAL CONDUCTOR FLAT CABLE HAVING A HEAD PORTION AND A BODY PORTION, SAID CONDUCTORS EXTENDING THROUGH SAID BODY PORTION AND HAVING FIRST ENDS TERMINATING IN SAID HEAD PORTION, II. INSULATING MEANS COVERING SAID BODY PORTION, III. A BREDGEWIRE FASTENED BETWEEN SAID CONDUCTORS IN SAID HEAD PORTION, IV. AN IGNITION MATERIAL COVERING SAID HEAD PORTION, AND IGNITION MATERIAL BEING COMPRISED OF ABOUT 90% BY WEIGHT OF A STOICHIOMETRIC MIXTURE OF LEAD THIOCYANATE ABOUT 35.6 PARTS, POTASSIUM CHLORATE ABOUT 44.4 PARTS, AND CHARCOAL ABOUT 20.0 PARTS, AND OF ABOUT 10% BY WEIGHT OF A BINDER MATERIAL COAPRISED OF LEAD STYPHANATE IN RATIO OF
 2. The match type electrical initiator of claim 1 wherein said conductors have second ends terminating outside said body portion. 